Hybrid and electric vehicles (HEVs) typically include an alternating current (AC) electric motor which is driven by a power converter with a direct current (DC) power source, such as a storage battery. Motor windings of the AC electric motor can be coupled to power inverter module(s) which perform a rapid switching function to convert the DC power to AC power which drives the AC electric motor, which in turn drives a shaft of HEV's drivetrain. Traditional HEVs implement two three-phase pulse width modulated (PWM) inverter modules and two three-phase AC machines (e.g., AC motors) each being driven by a corresponding one of the three-phase PWM inverter modules that it is coupled to.
Recently, researchers have investigated the possibility of replacing the two three-phase pulse width modulated inverter modules with a single five-phase PWM inverter module that simultaneously drives both of the three-phase AC machines. In addition, researchers have also investigated the possibility of using a single five-phase PWM inverter module that drives a first five-phase AC machine that is coupled to a second five-phase AC machine. One example of such research is described in a publication titled “Features of two Multi-Motor Drive Schemes Supplied from Five-Phase/Five-Leg Voltage Source Inverters,” by Dujić et al., May 27, 2008, which is incorporated by reference herein in its entirety.
While the possibility of using such inverter and motor configurations in HEVs is being explored, a lot of work remains to be done before these inverter and motor configurations can actually be implemented. One problem that has yet to be addressed is how to maintain the required output mechanical power of each machine while meeting voltage sharing constraints.
Accordingly, it is desirable to provide methods, systems and apparatus controlling operation of two AC machines that are controlled by a single five-phase PWM inverter module that allow constant output power with voltage constraint i.e. in the field-weakening region. It would also be desirable to provide methods, systems and apparatus for increasing the voltage used to drive the two AC machines. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.